"The degradation that happens in a blood sample over time
doesn't affect the iron. So a luminol test can be used on very
old, very dried blood samples and still give a very good
positive," criminal justice professor Nathan Lents,
who is not involved in the Avery case, told the TV
show.

"In fact, it actually gets better over time because some of
the agents that would interfere with the signal get degraded, but
the iron doesn't," he continued. "Iron doesn't go
anywhere."

Your browser does not support the video tag.
Pioneer ForensicsLuminol glows when used on a bloody shoe.

During Avery's trial, the prosecution alleged that Steven
and his then-teen nephew Brendan Dassey tortured and raped
photographer Teresa Halbach in Steven's room, and said she was
shot in the head in the garage. If all that actually
happened, the events probably left traces of
blood for luminol to detect — even if the scene was cleaned
up.

How does this help Steven? If no blood is detected by the
test, then it provides reason to believe that Halbach wasn't
killed in his home. If blood is found, then it will need to be
tested to try to find out whose it is.

Earl is optimistic about
Zellner. "Hopefully she does better than the
last two," he said, comparing Zellner to Steven's previous
lawyers, Dean Strang and Jerry Buting, who are prominently
featured in "Making a Murderer."
"They probably did a good job, but look at where [Steven] is,"
Earl added.

Steven and Dassey are both serving life sentences for
Halbach's murder.